1. Field of the Invention
The present invention relates to a cartridge which accommodates a recording medium within a case, and which is equipped with a write protect function for switching between a state in which recording onto the recording medium is possible and a state in which recording onto the recording medium is not possible.
2. Description of the Related Art
Cartridges, which accommodate a recording medium within a case, are used as external recording media of computers and the like. Specifically, the cartridge is structured such that a recording medium, such as a recording tape wound on a reel or a disc-shaped disk medium or the like, is rotatably accommodated within a case which is formed so as to be hollow by peripheral walls of an upper case and a lower case being brought into contact with each other.
A write protect portion for preventing data recorded on the recording medium from being deleted accidentally, is provided at the cartridge. A structure having an operation hole passing through the rear wall of the case which is at the side opposite to the side of loading the case into a drive device, a through hole provided so as to pass through the bottom plate of the lower case, and a switching member which, due to an operation projection which is exposed from the operation hole being operated from the outer side of the case, moves along the bottom plate so as to open and close the through hole (or one end portion of a long hole when the through hole is a long hole), is known as a write protect portion.
Namely, at the write protect portion, for example, the state in which the switching portion closes the through hole is a state in which recording onto the recording medium (a magnetic tape or the like) by the drive device is not possible, and the state in which the switching member opens the through hole is a state in which writing onto the recording medium by the drive device is possible. Thus, it is possible to selectively switch between the non-recordable state and the recordable state (to select the possibility/impossibility of recording).
The write protect portion has a detent structure. The detent structure is formed by an abutment member which is provided at one of the case and the switching member, and a flexible member which is provided at the other of the case and the switching member and is elastically deformable. In the state in which the switching member closes the through hole, the flexible member abuts one surface of the abutment member. In the state in which the switching member opens the through hole, the flexible member abuts another surface of the abutment member such that inadvertent movement of the switching member is prevented. When the operation projection is operated, the flexible member elastically deforms while maintaining the state of abutting the abutment member, and imparts a detent sensation (a “notching” sensation) to the operator.
As the detent structure, a structure is known in which the abutment member, which is formed in a mountain shape as seen in plan view, is provided at the switching member, and a detent pin serving as the flexible member stands upright at the ceiling plate of the upper case. In this structure, the detent pin is provided at the ceiling plate which does not interfere with the locus of movement of the switching member which moves along the bottom plate. Therefore, as compared with a structure in which the flexible member is provided at the lower case, the write protect portion can be made more compact on the whole.
As described above, the switching member is a member which switches selectively between the possibility and the impossibility of recording onto the recording medium. Thus, the switching member must be securely positioned at the closing position or the opening position of the through hole (i.e., the recording-impossible position or the recording-possible position), and this is achieved by the abutment member and the flexible member abutting one another.
However, in the above-described conventional cartridge in which the switching member having the abutment member opens and closes the through hole of the bottom plate and the detent pin is provided at the upper case, the detent structure is not formed until the upper case is joined to the lower case. Before the upper case is joined to the lower case, the switching member can move freely. Thus, if the switching member is positioned so as to be offset from the closing position or the opening position at the time when the upper case and the lower case are joined together, the detent pin will abut (interfere with) the abutment member. Such interference will not only impede the joining together of the upper case and the lower case, but also may be a cause of the detent pin breaking.
Thus, there are the problems that, when the upper case and the lower case are joined together, careful and complex work for ensuring that the position of the switching member is not offset is required, and the assemblability of the cartridge is poor.